Driving device and optical apparatus

Abstract

A lens driving device includes a stator, a rotor magnetized to have a plurality of poles, an arm fixed to the rotor in such a manner as to be rotatable together with the rotor, a moving member for rectilinearly moving a lens in response to a rotation of the arm and a coil for causing the stator to generate a magnetic flux to rotate the rotor.

What is claimed is: 
     
       1. A lens driving device, comprising: a stator;   a rotor magnetized to have a plurality of poles;   an arm fixed to said rotor in such a manner as to be rotatable together with said rotor;   a moving member for rectilinearly moving a lens in response to a rotation of said arm; and   a coil for causing said stator to generate a magnetic flux to rotate said rotor.   
     
     
       2. A lens driving device according to claim 1, wherein said moving member moves said lens along an optical axis thereof. 
     
     
       3. A lens driving device according to claim 2, wherein said moving member includes a holding member for holding said lens, a guide bar for guiding a movement of said holding member along said optical axis, and a clamping member provided on said holding member for clamping an end of said arm. 
     
     
       4. A lens driving device according to claim 3, wherein said clamping member clamps the end of said arm by elastic force. 
     
     
       5. A lens driving device according to claim 3, wherein said clamping member includes a pair of members each having a portion of arcuate cross-sectional shape which comes into contact with said arm. 
     
     
       6. A lens driving device according to claim 3, wherein said clamping member includes a pair of members each having a projection which comes into contact with said arm. 
     
     
       7. A lens driving device according to claim 1, wherein said rotor includes a rotating shaft having opposite ends, one end of which is of spherical shape, and a bearing having a tapered portion for receiving said one end of said rotating shaft, a thickness of said rotor which is taken along said rotating shaft being selected to be greater than a thickness of said stator which is taken along said rotating shaft, said one end of said rotor projecting from a corresponding end of said stator along said rotating shaft by a smaller amount than does another end of said rotor. 
     
     
       8. A lens driving device according to claim 1, wherein said stator includes a pair of stator portions forming a gap between opposed ends thereof in a direction perpendicular to said rotating shaft of said rotor, said pair of stator portions being disposed to surround said rotor and one of said pair of stator portions being inserted through said coil. 
     
     
       9. A lens driving device according to claim 8, wherein each of said pair of stator portions has a groove at a position which is 90° rotated from a position of said gap in a rotating direction of said rotor. 
     
     
       10. A lens driving device according to claim 9, wherein said groove is approximately equal to said gap in width. 
     
     
       11. A lens driving device according to claim 8, wherein each of said pair of stator portions has a groove at a position slightly offset from the position which is 90° rotated from the position of said gap in the rotating direction of said rotor. 
     
     
       12. A lens driving device according to claim 11, wherein said grove is approximately equal to said gap in width. 
     
     
       13. A lens driving device according to claim 1, wherein said rotor is magnetized to have two poles. 
     
     
       14. A lens driving device according to claim 1, further comprising detecting means for detecting a position of said lens, a supply device for supplying an electric current to said coil, and a controller for controlling said supply device according to an output of said detecting means. 
     
     
       15. A lens driving device according to claim 14, wherein said detecting means has a sensor for detecting a rotational position of said rotor. 
     
     
       16. A lens driving device according to claim 15, wherein said sensor has a magnetic sensor. 
     
     
       17. A lens driving device according to claim 16, wherein said sensor has a Hall element. 
     
     
       18. A lens driving device according to claim 16, wherein said rotor is magnetized in such a manner that a magnetic field strength detected by said sensor sinusoidally varies with a rotation of said rotor. 
     
     
       19. A lens driving device according to claim 18, wherein X=R·sin θ (R is a constant)   S=B·sin n  θ (B is a constant and n is an arbitrary natural number),   where θ represents the rotational position of said rotor, X represents the position of said lens, and S represents a magnitude of an output of said sensor.   
     
     
       20. A lens driving device according to claim 14, wherein said moving member is constructed so that a rotational angle of said rotor and an amount of movement of said lens can form a linear relationship. 
     
     
       21. A lens driving device according to claim 20, wherein said moving member includes a cam having a shape which is determined so that the rotational angle of said rotor and the amount of movement of said lens can form the linear relationship. 
     
     
       22. A lens driving device according to claim 21, wherein said rotor is magnetized in such a manner that a strength of a magnetic field generated from said rotor varies trapezoidally along a rotating direction of said rotor. 
     
     
       23. A lens driving device according to claim 14, wherein said controller controls said supply device according to an output value of said detecting means and an instruction value relative to the position of said lens. 
     
     
       24. A lens driving device according to claim 23, wherein said controller controls said supply device according to a difference between the output value and the instruction value. 
     
     
       25. A lens driving device according to claim 24, wherein said lens serves to form an image of a subject on a detecting face, and said controller controls said supply device so that a sufficient electric current to move said lens can be supplied to said coil when the difference between the output value and the instruction value corresponds to a deviation of not less than half of a radius of an allowable circle of confusion in terms of a state of the image on the detecting face. 
     
     
       26. A lens driving device according to claim 23, further comprising varying means for varying an output characteristic of said detecting means. 
     
     
       27. A lens driving device according to claim 26, wherein the output characteristic includes a gain. 
     
     
       28. A lens driving device according to claim 26, wherein the output characteristic includes an offset. 
     
     
       29. A lens driving device according to claim 26, wherein the output characteristic includes a gain and an offset. 
     
     
       30. A lens driving device according to claim 26, wherein said varying means varies the output characteristic according to a variation in temperature. 
     
     
       31. A lens driving device according to claim 30, wherein the output characteristic includes a gain and an offset. 
     
     
       32. A lens driving device according to claim 30, wherein X=R·sin θ (R is a constant)   S=B·sin n  θ (B is a constant and n is an arbitrary natural number),   where θ represents a rotational position of said rotor, X represents the position of said lens, and S represents a magnitude of the output of said detecting means.   
     
     
       33. A lens driving device according to claim 32, wherein said moving member is constructed so that a rotational angle of said rotor and an amount of movement of said lens can form a linear relationship. 
     
     
       34. A lens driving device according to claim 33, wherein said moving member includes a cam having a shape which is determined so that the rotational angle of said rotor and the amount of movement of said lens can form the linear relationship. 
     
     
       35. A lens driving device according to claim 34, wherein said rotor is magnetized in such a manner that a strength of a magnetic field relative to said rotor varies trapezoidally along a rotating direction of said rotor. 
     
     
       36. A lens driving device according to claim 1, wherein a rotational position of said rotor which corresponds to an intermediate position in a moving range of said lens is a position at which a torque generated in said rotor by said magnetic field reaches its maximum. 
     
     
       37. A lens driving device according to claim 36, further comprising a member for restricting a rotational range of said rotor. 
     
     
       38. A lens driving device according to claim 36, wherein a rotational range of said rotor is an electrical angle of 24° to 120°. 
     
     
       39. A lens driving device according to claim 1, wherein said lens is a focusing lens group of a zoom lens. 
     
     
       40. A lens driving device according to claim 1, wherein said lens is a zooming lens group of a zoom lens. 
     
     
       41. An optical apparatus arranged to move a lens of an optical system by using a lens driving device according to any one of claims 1 to 40.